The present invention relates to a power detector with increased detection range, intended primarily for use in radio links at higher frequency ranges.
In radio transmitters it is very important to be able to detect and control transmitted power, for example in order to be able to ensure that the transmitted power does not exceed permitted limit values, or in order to be able to transmit with just enough power for the receiving party to detect the signal with sufficient strength. On account of new advanced modulation forms, such as different variants of QAM (Quadrature Amplitude Modulation), for example 64-QAM or 128-QAM, it has also become extremely important to be able to control the output power with great accuracy over a wide dynamic range.
In order to detect transmitted power, so-called power detectors are used. A problem with known power detectors is that they have a limited dynamic range.
An aim of the present invention is thus to provide a power detector that can provide good accuracy over a wide dynamic range, in order to enable it to be used in different modulation types, for example different variants of QAM, for example 64-QAM and 128-QAM.
This aim is achieved by the present invention by the provision of a device for use for the detection of the power that passes through an electronic device, comprising means for division of the power that enters the device into a first and a second branch, each branch having a predetermined proportion of the total input power with a predetermined phase difference between the signals that go into the branches. The device according to the invention comprises in addition a first power detector for the first branch and a means for summation of the power in the two branches, and in addition the device comprises a second power detector for the second branch. The means for summation can be controlled with regard to which branch and thereby to which power detector the sum of the power is diverted, and the device comprises, in one of its branches, means for the said control of the summator.
The fact that the device according to the invention comprises two branches with a power detector per branch, and the fact that the sum of the power can be diverted to either branch, means that the two power detectors can be calibrated for different, preferably overlapping, parts of the dynamic range to be covered. In this way, if, for example, the first power detector is being used at a particular moment and detects that the power is about to go over into the range that is covered by the second detector, the power is diverted to the second detector, and vice versa. The fact that the two power detectors can be used for different dynamic ranges means in addition that, using two power detectors with limited dynamics, the invention can still achieve good accuracy over a wide dynamic range.
The means for division of the power and the means for summation both comprise suitably a summator, which makes it expedient to use a controllable phase shifter in the means for controlling the summator.
The invention can be used both in a transmitter of electromagnetic energy and in a receiver of electromagnetic energy, and also comprises a method for the use of a device according to the invention.